This invention relates to drum brakes for vehicles and more particularly to brake drum designs for cooler operation.
The conventional brake drum as shown in FIGS. 1, 2 and 3 has a solid cylindrical shape, and the internal surface (the internal diameter or “ID”) is a smooth, contiguous or unperforated cylinder against which the brake lining of a semicircular brake shoe (not shown) is frictionally engaged for braking. The images are for a 16.5×7 brake drum which is the most common size steel alloy or gray iron brake drum for heavy-duty tractors and trailers.
Brake drums are known to have been formed with external or internal fins to assist in cooling the drums. U.S. Pat. Nos. 3,127,959; 6,698,557 and 8,181,753 disclose various such approaches. The concept of drilling holes through the wall thickness of a braking surface has thus far been restricted to disc brake rotors, which are flat. However, this concept has never been applied to S-CAM brake drums which are a completely different braking system than disc brake rotors. For instance, the brake rotor system uses a caliper to squeeze a rotating disk, thus engaging the frictional surfaces. In contrast, the brake drum system uses an internal shoe to apply radial pressure to the cylindrical brake drum surface.
Brake fade occurs after repeated or sustained application of drum brakes which creates a high temperature condition and contributes to a reduction of stopping power. Significant improvement in brake performance can be obtained by optimizing the thermal performance of the brake drum. Although conventional brake drums continue to perform successfully in the field, a need remains for a brake drum design which maintains cooler temperatures than the conventional brake drum.